1. Field of the Invention
The present invention relates to a method of treating waste product containing flexible polyurethane resin, more specifically to a method of treating waste product processed by a volume reduction process using a chemical decomposition method and a reheating process for reproduction.
2. Description of the Related Art
Flexible polyurethane resin has been widely used as cushion material for vehicle seats, furniture, mattresses etc. However, recycling thereof is difficult because the resin is thermosetting and has a 3-dimensional network structure which cannot be remolded. Thus, used flexible polyurethane resin has been disposed of as landfill or incinerated after shredding without being recycled.
In waste processing of a used automobile, for example, after useful parts and the like are collected by a dismantler, scrapped cars are shredded, and, after removing metals such as iron for recycling, the remaining shredder residues of a vehicle seat are disposed of as landfill. However, the flexible polyurethane resin contained in the shredder residues, especially flexible polyurethane foam is bulky and contains bubbles that have a low density in the volume. Thus, there is a demand for reduction in the volume sort of the shredder residue by some method because the transportation cost is high even if the residue is disposed of as landfill, or if heat and resources are recovered by other methods.
Such a situation is not limited to the vehicle seat residues. Waste processing of cushion material which uses flexible polyurethane resins for sofas, chairs, mattresses etc, are in a similar situation, and thus there is a demand for a volume reduction method which is effective in reducing the transportation costs.
In addition to such a volume reduction, there is a demand for recycling of polyurethane resin in a waste product in order to effectively utilize resources in the future. On the other hand, studies have long been conducted on methods for chemically decomposing and liquefying polyurethane resins. For example, those methods include a method of decomposing a rigid polyurethane foam by an amine compound such as alkanol amine and then separating and recovering a decomposed product to reproduce it as a polyurethane foam, a method of decomposing a polyurethane foam with polyol and aminoethanol as decomposing agents and reproducing it as an adhesive agent, a ketone/aldehyde decomposition method, an isocyanate decomposition method, a thermal decomposition method, a hydrolysis method, a heating-up method in the latter process etc.
However, in the case where applying the aforementioned decomposition methods to the decomposition of the flexible polyurethane resin, the finally obtained decomposed product is separated into two phases, i.e., a solid body in a lower layer and a liquid polyol in an upper layer, irrespective of the kinds of decomposition methods used. The decomposed product thus separated into two phases has a reduced volume compared with a flexible polyurethane resin before decomposition, however, handling thereof is difficult, and carrying-in, carrying-out and transportation are complicated. Consequently, it is impossible to provide a sufficient reduction in transportation costs through a reduction in volume.